cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-9 of 9 results.

A048398 Primes with consecutive digits that differ exactly by 1.

Original entry on oeis.org

2, 3, 5, 7, 23, 43, 67, 89, 101, 787, 4567, 12101, 12323, 12343, 32321, 32323, 34543, 54323, 56543, 56767, 76543, 78787, 78989, 210101, 212123, 234323, 234343, 432121, 432323, 432343, 434323, 454543, 456767, 654323, 654343, 678767, 678989
Offset: 1

Views

Author

Patrick De Geest, Apr 15 1999

Keywords

Comments

Or, primes in A033075. - Zak Seidov, Feb 01 2011

References

  • J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 67, p. 23, Ellipses, Paris 2008.

Crossrefs

Cf. A010051; intersection of A033075 and A000040.

Programs

  • Haskell
    a048398 n = a048398_list !! (n-1)
    a048398_list = filter ((== 1) . a010051') a033075_list
    -- Reinhard Zumkeller, Feb 21 2012, Nov 04 2010
    (Python 3.2 or higher)
    from itertools import product, accumulate
    from sympy import isprime
    A048398_list = [2,3,5,7]
    for l in range(1,17):
        for d in [1,3,7,9]:
            dlist = [d]*l
            for elist in product([-1,1],repeat=l):
                flist = [str(d+e) for d,e in zip(dlist,accumulate(elist)) if 0 <= d+e < 10]
                if len(flist) == l and flist[-1] != '0':
                    n = 10*int(''.join(flist[::-1]))+d
                    if isprime(n):
                        A048398_list.append(n)
    A048398_list = sorted(A048398_list) # Chai Wah Wu, May 31 2017
  • Mathematica
    Select[Prime[Range[10000]], # < 10 || Union[Abs[Differences[IntegerDigits[#]]]] == {1} &]

A048405 Primes with consecutive digits that differ exactly by 8.

Original entry on oeis.org

2, 3, 5, 7, 19, 191, 919, 919191919, 91919191919, 91919191919191919, 91919191919191919191919, 191919191919191919191919191919191
Offset: 1

Views

Author

Patrick De Geest, Apr 15 1999

Keywords

Comments

The next term (a(13)) has 133 digits. - Harvey P. Dale, Jan 04 2023

Examples

			2 is a term since all its consecutive digits differ by 5 (there aren't any).
19 is a term because 1 and 9 differ by 8.
23 is not a term because its consecutive digits differ only by 1.
		

Crossrefs

Programs

  • Mathematica
    Module[{nn=500,nine,one},one=Select[Table[FromDigits[PadRight[{},n,{1,9}]],{n,nn}],PrimeQ];nine=Select[Table[FromDigits[PadRight[{},n,{9,1}]],{n,nn}],PrimeQ];Sort[Join[{2,3,5,7},nine,one]]] (* Harvey P. Dale, Jan 04 2023 *)

Extensions

Offset corrected by Sean A. Irvine, Jun 16 2021

A048400 Primes with consecutive digits that differ exactly by 3.

Original entry on oeis.org

2, 3, 5, 7, 41, 47, 14741, 14747, 74747, 1414741, 1474141, 7414741, 4141414747, 4147414147, 14141414141, 14141414741, 14141474741, 14141474747, 14147414741, 14147474141, 14147474147, 14741414747, 74141414147, 74141414741, 74147414741, 74741474741, 74747414141
Offset: 1

Views

Author

Patrick De Geest, Apr 15 1999

Keywords

Comments

All terms with more than a single digit must comprise only the digits 1, 4, and 7, because no number comprising the digits 2, 5, and 8 or the digits 3, 6, and 9 can be prime. - Harvey P. Dale, Mar 01 2023

Crossrefs

Programs

  • Mathematica
    Join[{2,3,5,7},Table[Select[FromDigits/@Tuples[{1,4,7},n],PrimeQ[#]&& Union[ Abs[ Differences[ IntegerDigits[ #]]]]=={3}&],{n,11}]//Flatten] (* Harvey P. Dale, Mar 01 2023 *)

Extensions

More terms from Naohiro Nomoto, Jul 28 2001
More terms from Sean A. Irvine, Jun 15 2021

A048401 Primes with consecutive digits that differ exactly by 4.

Original entry on oeis.org

2, 3, 5, 7, 37, 59, 73, 151, 373, 15959, 95959, 515951, 595159, 595951, 9515959, 51515159, 159595151, 159595951, 5151515951, 5159515159, 5159515951, 5951515151, 5951515951, 5959515151, 5959595951, 15151595951, 15951515159
Offset: 1

Views

Author

Patrick De Geest, Apr 15 1999

Keywords

Crossrefs

Programs

  • Mathematica
    pd[{a_,b_,c___}]:=Flatten[Table[Select[FromDigits/@Select[Tuples[ {a,b,c},n],Union[Abs[Differences[#]]]=={4}&],PrimeQ],{n,11}]]; Union[Join[{2,3,5,7},pd[{1,5,9}],pd[{3,7}]]] (* Harvey P. Dale, Aug 23 2011 *)

Extensions

More terms from Naohiro Nomoto, Jul 28 2001

A048402 Primes with consecutive digits that differ exactly by 5.

Original entry on oeis.org

2, 3, 5, 7, 61, 83, 383, 727, 72727, 94949, 1616161, 383838383, 727272727, 383838383838383, 38383838383838383, 72727272727272727, 94949494949494949, 383838383838383838383
Offset: 1

Views

Author

Patrick De Geest, Apr 15 1999

Keywords

Crossrefs

Programs

  • Mathematica
    Module[{nn=50,w1,w2},w1=Flatten[Table[Select[FromDigits/@Table[ PadRight[ {},n,{a,a+5}],{n,2,nn}],PrimeQ],{a,4}]];w2=Flatten[Table[Select[ FromDigits/@ Table[PadRight[{},n,{a+5,a}],{n,2,nn}],PrimeQ],{a,4}]];Join[ {2,3,5,7},w1,w2]//Union] (* Harvey P. Dale, Jan 09 2021 *)

A048404 Primes with consecutive digits that differ exactly by 7.

Original entry on oeis.org

2, 3, 5, 7, 29, 181, 929, 18181, 929292929, 18181818181818181818181818181818181818181818181818181818181818181818181818181
Offset: 1

Views

Author

Patrick De Geest, Apr 15 1999

Keywords

Comments

The next term (a(11)) has 163 digits. - Harvey P. Dale, Mar 23 2023

Crossrefs

Programs

  • Mathematica
    Module[{s18,s81,s29,s92},s18=Select[Table[FromDigits[PadRight[{},n,{1,8}]],{n,1,181,2}],PrimeQ]; s81=Select[Table[FromDigits[PadRight[{},n,{8,1}]],{n,2,182,2}],PrimeQ];s29 = Select[ Table[FromDigits[PadRight[{},n,{2,9}]],{n,2,182,2}],PrimeQ]; s92 =Select[Table[ FromDigits[ PadRight[{},n,{9,2}]],{n,1,183,2}],PrimeQ]; Join[{2,3,5,7},s18,s81,s29,s92]//Sort] (* Harvey P. Dale, Mar 23 2023 *)

A048403 Primes with consecutive digits that differ exactly by 6.

Original entry on oeis.org

2, 3, 5, 7, 17, 71, 1717171717171717171717171717171, 1717171717171717171717171717171717171
Offset: 1

Views

Author

Patrick De Geest, Apr 15 1999

Keywords

Comments

From Andrew Howroyd, Aug 13 2024: (Start)
Terms with more than 1 digit have digits alternating between 1 and 7.
No more terms < 10^3000. (End)

Crossrefs

Programs

  • PARI
    upto(limit)={my(L=List([t|t<-[2,3,5],t<=limit]),m=1); while(mAndrew Howroyd, Aug 13 2024

Extensions

Offset changed by Andrew Howroyd, Aug 13 2024

A089316 Prime worms [successive digit differences with absolute value of 2].

Original entry on oeis.org

131, 313, 353, 757, 797, 35353, 35753, 75797, 79757, 97579, 3131353, 3135313, 3531313, 7535797, 313131353, 313135313, 313579753, 353535313, 357531313, 357531353, 357535753, 357575753, 357975353, 753535357, 757975357, 975353579
Offset: 0

Views

Author

Enoch Haga, Dec 25 2003

Keywords

Examples

			a(4)=797; first and last digits are 7; abs(7-9)=2; abs(9-7)=2; the worm is 7.
		

Crossrefs

Cf. A089291.
This is a subset of A048399. Cf. A089291, A089315, A089317, A048398-A048405.

Programs

  • Mathematica
    pwQ[n_]:=Module[{idn=IntegerDigits[n]},First[idn]==Last[idn]&&Union[Abs[ Differences[idn]]]=={2}]; Select[Prime[Range[50000000]],pwQ] (* Harvey P. Dale, Mar 26 2013 *)

Formula

Select prime numbers having the same first and last digits; if the uniform absolute value of successive digit differences is 2, add to sequence.

A242846 Palindromic primes of the form ababa...aba containing only the digits 1 and 3.

Original entry on oeis.org

131, 313, 1313131313131313131313131, 313131313131313131313131313131313131313131313131313
Offset: 1

Views

Author

Felix Fröhlich, May 23 2014

Keywords

Comments

The next two terms both start with 3 and have 83 and 225 digits, respectively. Those are the only other terms with fewer than 352 digits. Cf. A062216.

Crossrefs

Programs

  • Mathematica
    Module[{nn=60,a,b},a=Table[FromDigits[Join[PadRight[{},2n,{1,3}],{1}]],{n,nn}];b=Table[FromDigits[Join[PadRight[{},2n,{3,1}],{3}]],{n,nn}];Select[Sort[Join[a,b]],PrimeQ]] (* Harvey P. Dale, Sep 07 2020 *)
Showing 1-9 of 9 results.